Preparation for cleaning metal preparatory to painting



Patented Jan. 31, 1939 UNITED STATES PATENT OFFICE PREPARATION FOR. CLEANING METAL PRE- PARATORY TO PAINTING Clete L. Boyle, Detroit, Mich.

No Drawing. Application February 26, I936, Serial No. 65,867

1 Glaim. (Cl. 148-8) This invention relates broadly to the art of application of water to the surface of the metal preparing metals for painting, lacquering, and or wiped off by the operator, and a true solution enameling, and specifically to an improvement in is removed more easily by rinsing or wiping. easa composition adapted to carry out such process. ily as against the difliculty which attends the 5 Heretofore it has been commonly the practice removal of the colloidal solutions. 5 to clean the metal with a rust removing acid, I have found that the addition of a certain such as sulphuric or phosphoric, in combination class of wetting agents to the rust attacking acid with a suitable oil solvent such as ethyl alcohol, oil solvent mixture will provide a solution which butyl alcohol, ethyl methyl ketone, or an ether will thoroughly wet the oil film and penetrate derivative of a dihydric alcohol, such as the the same and will disperse the solution over the 10 monobutyl ether of ethylene glycol. At times entire surface of the metal and will insure that viscosity or adhesive producing ingredients such the oil solvent and the acid carry out their inas sugar solutions, gelatine, glue, and similar tended functions. Furthermore, the mixture ingredients have been used to modify the physicontaining wetting agents of this class may be cal properties of the solution. These materials, mixed With Water in P p s Which v y 15 however, have very little modifying influence on substantially and still function satisfactorily. the regular acid solvent mixture for any worth- Various sulphonated hydrocarbons have been while purpose, suggested for use as wetting agents in cleaning In order that the acid may reach and attack compounds. Certain of these sulphonated prodthe rust on the metal, it is necessary that the ucts, such as sulphonated mineral oils or sul- 20 oil be removed from the surface of the metal. In phonated vegetable oils may function in certain order for the oil to be penetrated and dissolved cleaning compounds, such as alkaline or water for removal it is essential that the solution consolutions, but do not function satisfactorily in taining the oil solvent wet the oil covered surmetal cleaning acid solutions. Such sulphonated face of the metal. It is therefore desirable that products are not, in the metal cleaning acid so- 25 a solution be provided which will function to lutions, in such a state as to properly perform thoroughly wet the oil covered surface under any their wetting function. The environment is not and all working conditions. It is understood that such that a true solution is produced. The cleana concentrated mixture of the rust removing or ing solution so constituted may separate into etching acid and the suitable oil solvent is what distinct strata or assume a colloidal character 80 is sold to the manufacturer who then mixes the and the result is unsatisfactory. Some of these same with water in the desired proportions for sulphonated products may function fairly well in the cleaning operations to be carried on'. It is a very weak acid solution, but in cleaning comhighly desirable that this concentrated mixture pounds where the acid concentration is high,

3:, be miscible with water in varying proportions these wetting agents lose most of their effective- 85 and that the solution so resulting be capable of ness. satisfactorily performing its intended function. In the group of wetting agents, derivatives of While a relatively strong solution, such as not nitrogenous hydrocarbons or amines serve with to exceed two parts of water to one part of the unusual effectiveness as wetting agents in acid 40 mixture of the etching acid and the oil solvent, solutions and particularly in acid solutions of .3 functions satisfactorily to thoroughly wet the oil high concentration. These amines dissolve comcovered surface of the metal, weaker solutions pletely in the other ingredients of the cleaning flow over the oil surface without adhering or solution, namely, mono butyl ether of ethylene wetting the same and do not penetrate and disglycol, water and acid, 'to form a true solution solve the oil film. a therewith. When the acid solution containing 45 It is also desirable that a true solution as dissuch an amine is applied to the surface of the tinguished from a colloidal solution be formed as metal it spreads over and acts uniformly upon there is a tendency in colloidal solutions, more such surface. Such a solution will function to pronounced in some than in others, toward inthoroughly wet the surface of the metal and will stability and when this breaking down occurs on disperse thereover into crevices or joints which 50 the surface of the metal, the cleaning solution is might not be well covered by a workman in applyvery difficult to remove. It is to be understood ing the solution to the surface of the metal. that in these so called wet processes" of clean- It is not only desirable that the solution thoring metal, that the cleaning solution, following oughly wet the surface uniformly with a conthe cleaning operation, is either rinsed off by the tinuous film but that this characteristic of wet- 55 ness be not only uniform over the surface of the metal but that it retain such uniformity of distribution. If the cleaning operation is for any reason temporarily halted it is desirable that when the more volatile ingredients evaporate that the cleaning solution which remains on the surface of the metal be uniformly distributed thereover and does not form in streaks or spots where it is dispersed thereon.

Of the amine compounds the group of amino acids has been found to be particularly suitable as wetting agents in the metal cleaning acid solutions. These amino acids have an unusually great stability even in cleaning solutions of high acid content retaining their efllciency therein.

, Amino acids which have been found to be particularly suitable are the sulfanilic acids, which are also known as aminobenzenesulfonic acids, when they are further sulfonated with fuming sulphuric acid (known commercially as Oleum) to form aniline 2:4 disulphonic acid and this disulphonic acid is then alkylated by condensation with cetyl chloride to form dicetyl aniline 2:4 disulphonic acid. The structural formula for this compound is (C1sI-I:3)2NCsHa(SO:H) z, in which the sulfonic acid groups are in the 2 and 4 positions in the benzene nucleus with reference to the substituted amino group. Following this condensation it is preferable to convert this disulphonic acid into some soluble salt such as sodium dicetyl aniline disulphonate. Various other soluble salts such as the soluble salt of potassium or ammonium'may be used.

A mixture comprising orthophosphoric acid 60% by volume; monobutyl ether of ethylene glycol 30% by volume; and 10% by volume of a water solution of sodium dicetyl alkaline disulphonate (six ounces per gallon of water) answers, when mixed with water in the desired proportions, very satisfactorily the requirements of a good metal cleaning compound.

Instead of the above specifically referred to amino acid, toluidine disulphonic acids may be condensed with dicetyl chloride to form cetyl toluidine disulphonic acid from which soluble salts may be obtained as above described and employed in the same manner in the acid 011 solvent formula.

This concentrated mixture is mixed with water as desired by the user, and it has been found that it will function satisfactorily with as much as five parts of water to one part of the mixture. It is apparent that the strength or weakness of the solution may be varied as required by the cleaning operation to be performed.

It is understood that while the ingredients above specified in the proportions there set forth, represent a preferred formula that the relative percentages of these ingredients may be widely varied. Depending upon the character of the work to be encountered and the amount of water used, the amount of rust attacking acid used may be varied substantially. It might be reduced to 30% by volume in the solution set forth above.

The amount of oil solvent and the proportion of the wetting agent employed may each be proportionately changed to make up the concentrated mixture.

.Though orthophosphoric acid is here listed as the preferred metal etching acid because of its known desirable characteristics for the use in question, other well known rust removing or metal etching acids may be employed in its stead; likewise other well known oil solvents, certain ones having been heretofore set forth in patents issued to myself and James D. Klinger jointly; i. e., 1,545,498; 1,665,465; and 1,700,739; may be used in place of the mono-butyl ether of ethylene glycol.

What I claim is:

A solution to be used for'cleaning sheet metal preparatory to painting comprising a mixture of phosphoric acid, mono butyl ether of ethylene glycol, and a water solution of a sulphonated aniline in which the hydrogens of the amino group have been replaced by a long straight chain alkyl radicals such as are found in soap.

CLETE L. BOYLE. 

